, 11:51 AM
Glad to be of help.
For what it is worth I have leveled all three tanks to 50 and the one I use endgame in my Juggernaut Immortal/Vengeance hybrid. Here is my take on them.
Assassin: Played to perfection this is the most effective tank. It has great utility, awesome damage/threat, and if you know the fights and use all your cooldowns, self heals, etc is also the most survivable. However a poorly played sin is by far the least survivable tank and for that reason they have poor reputation.
Power Tech: The least complex of all the tanks. Also the most gear dependent as the majority of their survivability is passive. Lots of AoE damage which is good for trash fights and allows them to hold agro better then the Juggernaut. They have the worst defensive cooldowns which combined with their reliance on Shield/Absorption make them the worst PvP tanks.
Juggernaut: Combines the passive survivability of the Power Tech with the best general use defensive cooldowns (sins have the better cooldowns but they are very damage specific). Can be amazingly hard to kill but pays for it by having by far the worst damage/threat generation of any tank. Large groups can be incredibly frustrating to tank as a Juggernaut.
What I love about the juggernaut is their ability to move. Force Leap, Force Push, and Intercede work together to create a truly fun play style. However fun is wholly subjective and I have a friend who hates her jugg but loves her sin tank.
I also feel that the top half if the Juggernaut tanking tree is awful and use an Immortal/Vengeance hybrid. It has worse rage generation and AoE threat but better survivability and single target damage (Edit: I will be surprised if this spec survives the expansion and will be very sad when it comes unless a lot of improvements are made to the Immortal line).
A lot of the PT talents increase both damage and survivability so it can be easy to miss them. Here is a rundown of the survivability buffs you can get by lv50 from talents.
Combust: Lower the damage enemies do by 5% (active)
Rebraced Armor: +16% armor (passive)
Shield Vents: +2% Shield Chance (passive)
Oil Slick: Reduces enemies accuracy by 20% for 18 Sec, 1 min cooldown. (active)
Ablative Upgrades: +4% absorption and reduces the cooldown on Lolto Overload by 1 min. (passive and active)
Ion Screen: +2% damage reduction (passive)
Empowered Tech: +6% shield chance (passive)
Heat Screen: +8% absorption (active)
Power Armor: +2% damage reduction (passive)
Integrated Cargo Package: +3% Endurance (passive)